Rab8 attenuates Wnt signaling and is required for mesenchymal differentiation into adipocytes

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Mesenchymal stem cell differentiation into adipocytes is vital for metabolic health.
• Primary cilia and intracellular transport are essential for cell differentiation.
• Rab8 small GTPases regulate intracellular membrane trafficking but their role in mesenchymal differentiation is unclear.

Purpose of the Study:

• To investigate the physiological role of Rab8 GTPases in mesenchymal stem cell differentiation in vivo and in vitro.
• To elucidate the molecular mechanisms by which Rab8 influences adipogenesis.

Main Methods:

• Generation and analysis of Rab8a-deficient, Rab8b-deficient, and double-deficient mouse embryonic fibroblasts (MEFs).
• Immunofluorescence microscopy and biochemical assays to study protein localization and interactions.
• Assessment of adipocyte differentiation markers, including lipid droplet formation and Wnt signaling components.

Main Results:

• Rab8-deficient MEFs showed severely impaired adipocyte differentiation.
• Rab8 deficiency disrupted the vesicular compartment of Lrp6, impaired basal signalosome clearance, and affected frizzled two receptor traffic.
• Loss of Rab8 led to defective lipid droplet formation and abnormal cilia morphology during adipogenesis.
• Wnt signaling attenuation was compromised in Rab8-deficient cells.

Conclusions:

• Intracellular Rab8 traffic is essential for regulating adipogenesis induction in mesenchymal cells.
• Rab8 controls the proper localization of Wnt receptors, thereby modulating Wnt signaling during differentiation.
• These findings highlight Rab8's critical role in coordinating intracellular transport for adipogenesis.